POS0959 RISK FACTORS FOR NON-VERTEBRAL FRACTURES IN ANKYLOSING SPONDYLITIS
Authors: K. Bengtsson, J. Askling, M. Lorentzon, B. Rosengren, A. Deminger, E. Klingberg, L. T. H. Jacobsson, H. Forsblad-D’elia
Journal: Annals of the Rheumatic Diseases (2022)

Background Osteoporosis is common in patients with ankylosing spondylitis (AS) and a risk factor for fragility fractures. Additional established risk factors for fractures in the general population include higher age, female sex, previous fracture, fall tendency, glucocorticoid treatment, insulin dependent diabetes, smoking and high alcohol consumption. Objectives To estimate the influence of established risk factors for fragility fractures on the development of non-vertebral fractures in AS and population controls. Methods Through linkage of national population and health care registers 2001-2016, patients with AS (n=11611, 65.5% men, mean age 48 years) and age-, sex- and geography-matched population controls (n=58050) were identified and from 1 January 2007 (or 3 months after the first registered AS diagnosis if this occurred later) followed prospectively until the time of a non-vertebral fracture, death, emigration or end of study (30 December 2016). Occurrence of established risk factors for a fracture and AS related characteristics at start of follow-up were identified in the National Patient and Prescribed Drug Registers using ICD-10 and ATC codes. Smoking status and anthropometric measurements are not available in these registers. Chi-square, Fischer’s exact test and T tests were used to compare between subjects with and without a non-vertebral fracture during follow-up, separately for AS and controls. Multivariable Poisson regression was used to estimate the influence of each established risk factor in AS and controls. Risk factors for which there were ≤20 observed events in the AS cohort were not included. Results are presented as incidence rate ratios (IRR) with 95% confidence intervals. Results In total 974 (8.4%) patients with AS and 4106 (7.1%) of their controls were registered with a non-vertebral fracture during the study period. The characteristics of the patients and controls at start of follow-up are presented in Table 1 stratified by fracture status during follow-up. Figure 1 displays the results from the Poisson regression. Table 1. AS Controls No fracture (n=10637) Fracture (n=974) P-value No fracture (n=53944) Fracture (n=4106) P-value Male sex 7002 (65.8) 603 (61.9) 0.014 35448 (65.7) 2572 (62.6) &lt;0.001 Mean age (SD) 47.6 (14.7) 53.8 (14.8) &lt;0.001 47.8 (14.7) 53.0 (15.0) &lt;0.001 Prior fracture 667 (6.3) 140 (14.4) &lt;0.001 2715 (5.0) 486 (11.8) &lt;0.001 Osteoporosis* 359 (3.4) 83 (8.5) &lt;0.001 367 (0.7) 85 (2.1) &lt;0.001 Fall injury without fracture 714 (6.7) 97 (10.0) &lt;0.001 3205 (5.9) 350 (8.5) &lt;0.001 Harmful use of alcohol 158 (1.5) 26 (2.7) 0.005 889 (1.6) 171 (4.2) &lt;0.001 Hyperthyroidism 39 (0.4) 7 (0.7) 0.105 180 (0.3) 19 (0.5) 0.173 Diabetes type 1 178 (1.7) 30 (3.1) 0.002 651 (1.2) 80 (1.9) &lt;0.001 Liver disease 66 (0.6) 10 (1.0) 0.132 197 (0.4) 32 (0.8) &lt;0.001 Malnutrition 8 (0.1) 3 (0.3) 0.058 16 (0.0) 2 (0.0) 0.367 Hypogonadism or premature menopause 11 (0.1) 1 (0.1) 1.000 33 (0.1) 0 (0.0) 0.169 Use of oral glucocorticoids # 1531 (14.4) 152 (15.6) 0.304 839 (1.6) 97 (2.4) &lt;0.001 Anterior uveitis 2168 (20.4) 204 (20.9) 0.677 317 (0.6) 32 (0.8) 0.126 Psoriasis 316 (3.0) 34 (3.5) 0.364 605 (1.1) 58 (1.4) 0.091 Inflammatory bowel disease 675 (6.3) 64 (6.6) 0.783 441 (0.8) 35 (0.9) 0.811 Use of any DMARD ¤ 3411 (32.1) 266 (27.3) 0.002 465 (0.9) 52 (1.3) 0.008 Use of TNF inhibitor ¤ 1539 (14.5) 109 (11.2) 0.005 43 (0.1) 4 (0.1) 0.573 The data is presented as number (%) if not stated otherwise. *Diagnosed osteoporosis and/or use of osteoporosis medication. # Prednisolone equivalent cumulative dose of ≥450 mg within the last year before start of follow-up. ¤ Use within the last year before start of follow-up. Figure 1. Multivariable Poisson regression analyses for a non-vertebral fracture during follow-up, with results presented for each included baseline variable as IRR with 95% CI, separately for AS and controls. Conclusion The influence of established risk factors for fragility fractures in AS is similar to that in the general population; in both populations with advanced age, prior fracture and harmful use of alcohol being the strongest risk factors. Disclosure of Interests Karin Bengtsson: None declared, Johan Askling Grant/research support from: AbbVie, AstraZeneca, Bristol Myers Squibb, Eli Lilly, Janssen, Merck, Pfizer, Roche, Samsung Bioepis, Sanofi, and UCB, Mattias Lorentzon: None declared, Björn Rosengren: None declared, Anna Deminger: None declared, Eva Klingberg: None declared, Lennart T.H. Jacobsson Speakers bureau: Lecture and consulting fees from Novartis, Eli Lilly and Janssen, Helena Forsblad-d’Elia: None declared